The invention relates to the transmission of binary signals and, more particularly, to a system for the transmission of a main pulse train having a frequency of F, and of two derived pulse trains, having respective frequencies of F/N and of F/k.N (where k and N are positive integers 1, 2, . . . ) the pulses of the derived pulse trains being arranged not to coincide with one another, the system comprising a transmitter, a transmission channel and a receiver.
When digital data is transmitted, a distinction is often made between "bit" synchronization and "frame" synchronization, the data being grouped together in a digital train in blocks or frames of N bits. To obtain correct synchronism between two units of equipment, not only must a bit synchronizing signal be transmitted, but other synchronizing signals must also be transmitted, e. g. for frame synchronization. According to a known technique, a distinct transmission path, e. g. a pair of wires or a channel in a multiplex, is provided for the transmission of each synchronizing signal.
It has already been proposed to reduce the number of transmission paths used for synchronization by grouping together a main pulse train and a derived pulse train in a single bipolar channel. The pulses of the derived pulse train are transmitted as violations of the bipolarity of a bipolar pulse train having a frequency F.